Deionizers with energy recovery

ABSTRACT

Deionizers using the electrode configurations of electrochemical capacitors are described, wherein the deionizing process is called capacitive deionization (CDI). During deionization, a DC electric field is applied to the cells and ions are adsorbed on the electrodes with a potential being developed across the electrodes. As electrosorption reaches a maximum or the cell voltage is built up to the applied voltage, the CDI electrodes are regenerated quickly and quantitatively by energy discharge to storage devices such as supercapacitors. In conjunction with a carousel or Ferris wheel design, the CDI electrodes can simultaneously and continuously undergo deionization and regeneration. By the responsive regeneration, the CDI electrodes can perform direct purification on solutions with salt content higher than seawater. More importantly, electrodes are restored, energy is recovered and contaminants are retained at regeneration, while regeneration requires no chemicals and produces no pollution.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation-in-pat of U.S. patentapplication Ser. No. 09/948,852, filed Sep. 7, 2001. The presentapplication is also a continuation-in-part of U.S. patent applicationSer. No. 09/784,718, filed Feb. 15, 2001. Both prior applications areincorporated herein by reference. References Cited 4,765,874 August 1988Modes et al. 4,991,804 March 1991 Pekala 5,779,891 July 1998 Andelman5,858,199 January 1999 Hanak 5,954,937 September 1999 Farmer et al.6,051,096 April 2000 Nagle et al. 6,168,882 January 2001 Inoue et al.6,267,045 July 2001 Wiedemann et al. 6,309,532 October 2001 Tran et al.6,326,763 December 2001 King et al. 6,328,875 December 2001 Zappi et al.

OTHER REFERENCES

[0002] J. Newman et al, J. Electrochem. Soc., 128, PP510-517(1971),“Desalting by Means of Porous Carbon Electrodes”

[0003] I. Parikhi; P. Cuatrecasas, C&EN, Aug., 26, 1985, PP17-32(1985),“Affinity Chromatography”

BACKGROUND OF THE INVENTION

[0004] 1. Field of Invention

[0005] This invention relates generally to capacitive deionization (CDI)of liquids containing charged species, including aqueous, inorganic andorganic solutions. More particularly, this invention relates torecurrent electrosorption of ions (deionization) and regeneration ofelectrodes whereby energy is extracted and stored in supercapacitors,ultracapacitors, or electric double layer capacitors. The presentinvention provides deionizors wherein purified liquids and electricityare co-generated.

[0006] 2. Description of Related Art

[0007] Energy and water are two essential ingredients of modern life.Since the fossil fuel is diminishing and generates pollution at powergeneration, people become more eager in searching for alternativesources of energy. Therefore, renewable energy sources such as solarpower, wind power, wave power, and geothermal heat have been exploredand commercialized. Many international automakers are aggressivelydeveloping fuel cells for pollution-free electric vehicles. All of theabove endeavors are aimed to reduce CO₂ emission and to use natural freeresources such as sun and water for energy production. Production ofenergy is no easy matter, hence conservation of energy that includescontrolled usage and responsive extraction of energy deserves attention.There are numerous viable ways for retrieving residual energy that wouldbe otherwise wasted. For example, U.S. Pat. No. 6,326,763 issued to Kinget al disclosed a regenerative braking system that can store electricityconverted from the remaining momentum of vehicle during periods ofdeceleration due to braking for stop or moving down hill.Ultracapacitors were proposed in '763 to extract the residual energythat is generally dissipated as heat. In another example, U.S. Pat. No.6,267,045 issued to Wiedemann et al revealed a cooking device containingan energy storage and energy extraction system wherein energy isexchanged in the form of latent heat.

[0008] Less than 1% of water on the earth surface is suitable for directuse. Fresh water will be one of the precious commodities in the 21stcentury. In lieu of rainfall, desalination of seawater is probably themost plausible means to attain fresh water. Among the commercialdesalination methods, distillation dominates the market with 56% share,reverse osmosis (RO) possesses 40%, while freezing and electrodialysisseize the rest. The aforementioned methods though are different in thepurification mechanisms, they are all utilized to reduce the totaldissolved solids (TDS) which is a measure of charged species insolutions so that seawater can become potable. Reduction of TDS, ordeionization, is also an ultimate goal for waste liquid treatments whereion exchange and RO are most frequently used. In purifying seawater orwaste liquids, the employed method should be a low energy-consumption,pollution-free, and long service-life technique. In fulfilling theforegoing requirements, capacitive deionization (CDI) is a superiormethod than ion exchange, RO, and other techniques for deionization.There are five reasons to vindicate the supreme merit of CDI: (1) CDIuses a DC electric field for adsorbing and removing ions from solutions,the process is quick and controllable with minimal energy consumption.(2) Energy that is input for electrosorption can be extracted and storedfor latter use or other applications. No energy recovery is available inany of the aforementioned separation methods. (3) While energy istransferred from the CDI electrodes to a load, the electrodes arerestored simultaneously. Regeneration of CDI electrodes by energyextraction is prompt without using chemicals and without producingpollution. (4) CDI can directly deionize seawater or solutions with TDShigher than 35,000 ppm. Deionization and regeneration can be repeatednumerous times until the liquids are clean, and the electrodes are notdegraded by the high salt content. Whereas RO, electrodialysis, and ionexchange are better utilized for treating low salt-content solutions.Otherwise, their expensive membranes or resins will be damaged quickly.(5) Ions that are adsorbed by the CDI electrodes can be discharged in aconcentration reservoir for recycling useful resources or for sludgedisposal. Extraction of ions by CDI is a non-destructive process, thussome ions may be processed for reuse. The invention will demonstrate allof the foregoing five unique features of the CDI technique in the lattersection of detailed description. Incidentally, energy recovery in thedeionizers is consistent with the ultimate principle of free energytapping, that is, no fuel should be added and no pollutant should beemitted.

[0009] CDI is a separation methodology that is known for more than 40years (J. Newman et al, 1971). Just to name a few, U.S. Pat. Nos.5,799,891, 5,858,199, 5,954,937 and 6,309,532 are all intended tocommercialize the CDI technique. Particularly, '532 issued to Tran et aldisclosed the use of electrical discharge for regenerating electrodes.Rather than reclaiming the residual energy, the electricity isdissipated by shorting or reverse polarity (claims 4, 18, 21, and 23).Shorting a fully charged capacitor may cause electrical hazardsparticularly when the energy accumulated is immense. It is known topeople skilled in the art that reverse polarity would momentarily expelthe adsorbed ions from the electrodes. However, the ions would leave oneelectrode and then be adsorbed by the other electrode, unless analternate polarity reversal of appropriate frequency is applied inconjunction with a large quantity of fluid for flushing the desorbedions out of the cell. This may explain why 40 liters of liquid was usedfor every cycle of regeneration in Example 1 of '532. In addition, onecycle regeneration of the CDI electrodes of '532 takes several hours toaccomplish, such lengthy process is unprofitable for commercialapplication. As indicated by FIG. 12 of '532, deionization as proposedwas equally slow as a reduction of TDS by 59 ppm (100 μS divided byconversion factor 1.7) using 150 pairs of 10×20 cm² electrodes, or atotal geometric area of 30,000 cm², took 10 minutes of processing time.Moreover, '532 taught a serpentine liquid flow pattern in a complex cellas shown by FIG. 3 wherein 150 pairs or other combination of electrodeswere stacked and compressed. For creating the liquid path, apertureswere specifically fabricated on the electrode supports whereon carbonaerogel, lithographically perforated metal, or costly metal carbideswere used as the electrosorptive medium. Usage of the foregoing designsand materials will add cost to the CDI cells and present difficulties tooperation, as well as maintenance. In comparison, disclosures of thepresent invention will furnish cost-effective, high-throughput, anduser-friendly deionizers for purifying contaminated liquids and fordesalinating seawater. After partial or complete adsorption of ions, thedeionizers can be discharged at different rates to deliver constantcurrents or peak currents to different loads as required. In otherwords, the deionizers can be utilized as liquid purifiers, asenergy-storage devices, and as power converters.

SUMMARY OF THE INVENTION

[0010] Practically, CDI has adopted the charging mechanism ofsupercapacitor (other nomenclatures for the device includeultracapacitor and electric double layer capacitor) for removing ionsfrom solutions in this invention. Supercapacitor is an electrochemicalcapacitor that can store static charges up to several thousands of farad(F), and it can be charged and discharged quickly. As the electrodes ofsupercapacitor accumulate ions on their surface, a DC potential isdeveloped with increasing charges across the positive and negativeelectrodes of the capacitor. Such voltage rise with ion accumulationrelationship is also observed during deionization by CDI process.Therefore, voltage can be used to determine if the CDI electrodes havereached an adsorption maximum, or they have reached an equilibrium statewhere the induced potential is equal to the applied voltage. In eithercase, the CDI electrodes require regeneration for further service.Following the general electrode configurations of supercapacitors, thatis, stacking or winding, the CDI electrodes are similarly constructedand assembled into modules but with two variations. Firstly, unlike theseparators reserve electrolytes for the supercapacitors, componentsother than the electrosorptive medium in the CDI modules should neitheradsorb nor retain ions. Secondly, unlike the electrodes ofsupercapacitors are enclosed in protecting housings, the CDI electrodesare merely secured by simple means such as tape without encapsulation.Hence, the CDI electrodes of the present invention are widely open tothe surroundings, and fluids to be treated have free access to theelectrodes. With the foregoing flow-through design, the CDI modules canbe placed in fluid conduits for deionization, or they can be submergedin liquids and cruised like a submarine to remove ions.

[0011] Not only the electrodes are assembled using the minimal amount ofsupporting materials, readily available activated carbon of low price isalso used as the electrosorptive medium for further reducing the cost ofCDI modules. Carbon material is deposited onto an electricallyconductive substrate by an inexpensive process such as roller coating toform the CDI electrodes. With cost-effective materials, easy fabricationof electrodes, and simple assembly of electrodes, the deionizers canbecome reliable consumer products affordable to families and industries.

[0012] Just like the stored energy of supercapacitors can be quicklyextracted via discharge, the residual energy of the CDI electrodes afterelectrosorption of ions is also available for fast tapping. Though theenergy that is reclaimed is far less than the energy that is input fordeionization, the residual energy is free and addible for practicalapplications. Besides, same as the supercapacitors having 100% dischargedepth, the energy stored on the CDI electrodes can be completely drainedas well, and the electrodes are thoroughly cleaned as a consequence ofenergy recovery. To store the residual energy reclaimed from the CDImodules, supercapacitors, or ultracapacitors, or electric double layercapacitors are particularly well suited as the storage devices. This isdue to the devices are more efficient in storing energy than otherdevices such as batteries and flywheels. As long as the source voltageis higher than the voltage of supercapacitors, the capacitors can alwaysbe charged regardless of the magnitude of charging current. When the CDImodules are installed on a carousel or Ferris wheel, the electrodes canthen be reciprocally and continuously engaged in deionization andregeneration. Because of swiftly recurrent deionization andregeneration, the deionizers have high throughputs for purifyingcontaminated liquids as well as for desalinating seawater. It isexperimentally observed that the repeated deionization and regenerationcause no damage to the deionizers.

[0013] Restoration of the CDI electrodes by energy extraction isoperational in any liquids including seawater. Only the adsorbed ionsare discharged to a liquid, thus the liquid has no influence onregeneration and there is no second pollution. Furthermore, no flushingliquid or regenerant fluid is required to discharge the ions for theyare automatically dissipated at energy recovery. Except a minimal amountof clean liquid may be needed to rinse the electrodes, the regenerationproduces no waste liquid. Ions are adsorbed by the CDI electrodes undera DC electric field whereby the applied voltage can be controlled belowthe decomposition potentials of ions. Thence, the CDI electrodes may beutilized as a magnet to non-destructively take ions out of liquids andto place them in a concentrating container. Once the ions areconcentrated in a small volume of liquid, useful resources can be easilyrecycled or the sludge can be effectively disposed. It is during theperiod when the restored electrodes are returned from the concentratingcontainer to the deionization chamber that rinsing may be required.

[0014] Deionization of solutions by CDI only requires the application oflow DC voltages, thus it is operable by batteries, fuel cells, and solarcells. Most of the latter devices have poor power densities.Nevertheless, after the residual energy is stored in supercapacitors,the capacitors can then deliver peak powers to various heavy loads. Fromthis aspect, the deionizers behave as power converters using adsorptionand desorption for energy transference. Because of various electricalresistances and other forms of energy loss such as electrolysis, thecycle of adsorption and desorption, or charge and discharge is not aperpetual motion. Nevertheless, using the deionizer of this invention asa power converter may provide some practical applications.

[0015] It is to be understood that both the foregoing generaldescription and the following detailed description are exemplary, andare intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings are included to provide a furtherunderstanding of the invention, and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention. In the drawings,

[0017]FIG. 1A is the first top view of two CDI electrode modulesinstalled in a two-compartment carousel. One compartment is designatedfor deionization, and the other for regeneration. As the carouselrotates, the regenerated electrode module will perform deionizationwhile the saturated module will undergo regeneration.

[0018]FIG. 1B is the second top view of the two-compartment carousel. Itshows one electrode module can receive electricity from power supply Bfor deionization, and the other module can release its residual energyto load C.

[0019]FIG. 2A is a side view of two CDI electrode modules installed in aFerris wheel. The wheel has both lifting and rotating mechanisms thatcan switch the modules from deionization to regeneration, or fromregeneration to deionization as required. Using the Ferris wheel design,only a few sets of CDI modules are sufficient for purifying contaminatedliquids and for desalinating seawater.

[0020]FIG. 2B is a top view of a Ferris wheel containing 8 compartmentsand 8 CDI modules. The compartments are divided into three zones fordeionization, regeneration, and post-treatment.

[0021]FIG. 3 is a side view of another type of Ferris wheel where aconveyor carrying cylindrical CDI modules. There are three sections fordeionization, regeneration, and post-treatment.

[0022]FIG. 4 is a control module that is composed of a step-upcircuitry, a microprocessor and a supercapacitor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] There are two major functions by which activated carbon removescontaminants from liquids, and they are surface adsorption and catalyticreduction. Adsorption generally occurs via some kind of affinity betweenthe contaminants and the adsorbing surface. Since the adsorptive forcesare weak and the adsorption is subject to a slow thermodynamic control,activated carbon has to rely on its large surface area and theinfinitesimal proximity between its surface and the contaminants formassive purification. However, under the application of a DC electricfield, adsorption on activated carbon can be expedited. Also, due to thepolarity built on the surface of activated carbon, the carbon willadsorb ions of opposite polarity and a selective adsorption is created.With large surface area, the charged carbon can quickly adsorb a largenumber of ions. Even without the application of an electrical field, theadsorbed ions can still remain on the surface of activated carbon for aperiod of time. The foregoing features make activated carbon attractiveas an electrosorptive material for liquid purification. Large surfacearea is the primary reason that activated carbon is commonly used forfabricating energy-storage devices such as supercapacitors, as well asfor deionization and desalination. Other considerations that activatedcarbon is preferred include inert nature, wide availability, maturetechnology, and low price. In addition, when carbon nanotube (CNT) isavailable in large quantity of suitable cost, CNT would be another idealcandidate as the electrosorptive material for the CDI electrodes.

[0024]FIG. 1A shows a preferred embodiment of the invention wherein twoelectrode modules consisting of 7 pairs of electrodes each are placed ina two-compartment carousel 10. The compartment 12 contains a liquid 20to be treated and a first electrode module having electrodes connectedin parallel to form an anode 16 and a cathode 18, respectively. By usingelectrical cables, the anode 16 and the cathode 18 are connected to thecorresponding positive and negative poles of a DC power source B,electricity is then supplied to the module for deionizing the liquid 20.Similarly, the compartment 14 contains a liquid 24 as a regenerationmedium and a second electrode module, which had been used fordeionization, for discharging its residual energy to load C through ananode 16′ and a cathode 18′. The liquid 24 can be a clean solvent or thesame liquid as 20 to provide a medium for the adsorbed ions to bedischarged. The medium will have no influence on ion discharge or energyextraction. The carousel 10 has a motor (not shown) built at the bottomof a central pole 22 for rotating the electrode modules in the directionindicated by A. As soon as one module is saturated and the other isfully restored, they will be switched positions for a new cycle ofelectrosorption and regeneration. Before rotating the carousel, theliquids 20 and 24 are drained (liquid conduits and control valves arenot shown) so that new liquids of 20 and 24 can be refilled into thecompartments 12 and 14 for deionization and regeneration, respectively.If the liquid 20 has a low salt content and can be purified in one cycleof deionization, the purified liquid is retreated for use or fordisposal to sewer. Whereas the liquid 24 can be recycled indefinitely tocollect ions released during regeneration.

[0025] Another preferred embodiment of provision for the recurrentdeionization and regeneration, or sorption and desorption, is by liftingthe electrode modules up and switching their positions for deionizationand regeneration. In this operation, both chambers 12 and 14 as well asliquids 20 and 24 are stationary so that the liquid 20 can becontinuously deionized until it is acceptable for release, while theliquid 24 can be used for receiving the released ions indefinitely. Ifnecessary, the restored CDI module may be rinsed with a pure liquidbefore being placed back for the next run of deionization. Afterrinsing, the waste liquid may be added to the reservoir of liquid 24 asa regeneration medium. Though only two compartments and two electrodemodules are shown in FIG. 1A, other numbers of compartments and CDImodules can be used to meet application needs. Using recurrentdeionization and energy extraction, the present invention can thusco-generate purified liquids and electricity.

[0026] As shown in FIG. 1A, the modules comprise 7 pairs of stackingelectrodes connected in parallel. There is an insulating spacer in theform of screen, mesh, net, network, web or comb (not shown) interposedbetween every two electrodes to prevent electrical short. To serve itspurpose, the spacer should be inert, non-adsorptive, and non-leachable.Materials such as PE (polyethylene), PP (polypropylene), PVC, Teflon andNylon may satisfy the foregoing requirements. Preferably, the spacershould have a width smaller than 0.2 mm, preferably from 0.05 mm to 0.1mm, to allow free pass of liquids. Activated carbon made from precursorssuch as coconut shell, pitch, coal, polyurethane, and polyacrylonitrile(PAN) can be employed as the electrosorption medium. Moreover, carbonnanotube (CNT) with appropriate tube diameters, for example, from 2 nmto 50 nm, is an ideal material for preparing the CDI electrodes. Mixedwith a fluorinated binder and a solvent, powder of activated carbon orCNT is converted to a homogeneous paste suitable for roller coating onsubstrates. Titanium foil of 0.05 mm or less is used as the substratefor anodes, while copper foil of 0.02 mm or less for preparing thecathodes. Suitable metal leads are attached to the electrodes by spotwelding or soldering. Electrodes are then stacked with a screen spacerdisposed between every two electrodes. Using an insulating tape, or twoplastic plates and at least two bolts and two nuts (not shown in FIG.1A), the whole stack of electrode and spacers are secured to form a CDImodule. Assembled without encapsulation as aforementioned, the modulemay be submerged in liquids to be treated for deionization. In addition,if the electrodes and spacers can be spirally wound into an open roll,it can be installed in conduits for deionizing liquids that flow freelythrough the electrodes. The CDI electrodes may be connected in parallelfor higher surface area, or in series for higher applied voltage, or inhybrid mode for a special need.

[0027]FIG. 1B is another top view of the deionizer with energy recovery.B is a DC power source that includes rectified AC power, batteries,solar cells, and fuel cells. Only a DC voltage of 1˜3V is required tosustain electrosorption of the CDI module in compartment 12 of carousel10. However, a higher voltage may be used to provide bothelectrosorption and electrolysis with benefits more than justdeionization. As disclosed in U.S. Pat. No. 6,328,875 issued to Zappi etal, which is incorporated herein as reference, disinfection ofmicroorganisms and organic pollutant was realized by using electrolysis.Occasionally, electrolysis may be utilized to generate oxidants toprevent fouling of the CDI electrodes. Nevertheless, the presentinvention is primarily designed for deionization, and electrolysis isgenerally avoided. Block 26 is a microprocessor that performs threefunctions: (1) to monitor the potential developed across the electrodesof CDI modules; (2) to activate and deactivate the motor of carousel;and (3) to regulate energy extraction. Load C can extract the residualenergy from the CDI module in compartment 14, whereby the CDI module isrestored at the same time, through anode 16′ and cathode 18′. It ispreferably to store the reclaimed energy in devices such assupercapacitors, ultracapacitors, or electric double layer capacitors.Because all of the foregoing capacitors are cable of accepting anymagnitude of current without mechanical movement, they have bettercharging efficiency than batteries and flywheel. Moreover, thecapacitors can be fabricated more compact than flywheel. As thepotential developed across the electrodes of capacitors equals thesource voltage, energy transfer will be ceased. At this point, the CDImodule may not be completely regenerated for some residual energy isstill present on the electrodes. One way to solve the problem is byusing a power bank consisting of many capacitors, or an electronicenergy-extractor. In order to minimize loss at energy extraction, theinternal resistance or ESR (equivalent series resistance) of thesupercapacitors should be as low as possible.

[0028]FIG. 2A is a side view of yet another preferred embodiment ofarranging a deionizer with energy recovery in Ferris wheelconfiguration. For the purpose of simplification, only two compartments205 and 207, as well as two CDI electrode modules 213 and 215 are shownin container 201. Other accessories including power source,microprocessor and load are omitted for they are similar to those inFIG. 1B. Ferris wheel 200 has motors built inside the central pole 213to provide lifting motion for the lever 203 with electrode modules 213and 215 from position A to position B, and to switch the CDI modulesfrom deionization to regeneration or vice versa. Nevertheless, thedistance between A and B is not drawn to reflect the real size thatallows enough clearance for the CDI modules to be rotated. Compartment205 is designated for regeneration wherein a pure liquid or the samesolution as liquid to be treated in compartment 207 is used indefinitelyas regeneration medium. Compartment 207 is designated for deionizationwherein contaminated liquids or seawater can enter the compartment byinlet 209 and exit the compartment from outlet 211 once they arepurified. Due to two simple movements are demanded, motors of Ferriswheel 200 should consume little amount of energy and they may beoperated by the same power source that sustains deionization.

[0029]FIG. 2B shows a Ferris wheel 400 containing 8 compartments with 8CDI modules represented by 408. On each module, there is a controlmodule represented by 402 containing a microprocessor and a step-upcircuitry for draining the residual energy of the CDI module. Eachmodule is mounted to a lever represented by 203 where a control moduleis disposed on the top of the CDI module. The control module can monitordeionization, activate and deactivate mechanical movements, as well asregulate energy extraction. There are motors built inside the centralpole 217. The compartments are divided into 4 sections where 404 is fordeionization, 406 for regeneration, areas A and B are waiting quartersfor the CDI modules to be treated for minimizing cross contamination.

[0030]FIG. 3 is still another preferred embodiment wherein a moving belt37, which is engaged by rollers represented by 38, carrying a number ofCDI modules represented by 33 in cylindrical form for recurrentdeionization and regeneration. Both liquids to be treated 31 andregeneration medium 35 can flow freely through the CDI electrodes. Afterdeionization, fluent 32 may become a purified liquid, while fluent 36will be enriched by the ions discharged at regeneration. As in FIG. 2B,each CDI module is equipped with a control module represented by 34.Area labeled 40 is the waiting quarter where the CDI modules arepost-treated to reduce cross contamination.

[0031]FIG. 4 is the diagram of the foregoing control module that iscomposed of a step-up circuitry S, a microprocessor PWM and asupercapacitor L. In FIG. 4, B is a DC power source to provideelectricity to CDI for deionization. Then, the residual energy of CDIcan be discharged via S to supercapacitor L. Normally, S is off untilthe potential of CDI is equal or smaller than the voltage of L. When thelatter situation occurs, microprocessor PWM will raise the potential ofCDI through S to above the voltage of L to completely drain the residualenergy of CDI. Using an electronic energy extractor as PWM and S,electrodes of CDI can be quickly restored. The microprocessor PWM alsoactivates and deactivates motor M so that the CDI modules can beswitched to the desired positions.

[0032] Instead of using an automatic carousel or Ferris wheels setup,the CDI modules in the following examples are switched betweendeionization and regeneration manually. Experimental are presented todemonstrate that the CDI modules can 1) directly purify seawater orwaste liquids with higher salt content; 2) undergo numerous cycles ofsorption and desorption without degradation; and 3) convert the powerdensity of a power source.

EXAMPLE 1

[0033] A CDI module is composed of 4 cells connected in series whereineach cell consists of 2 parallel electrodes with a PVC screen disposedin the middle. Each electrode has a dimension of 6 cm×5 cm×0.35 mm anduses one activated carbon (surface area 1050 m²/g at $0.30 per pound) asthe electrosorptive medium. The module is placed in seawaters ofdifferent salt content, namely, 5,000 ppm, 20,000 ppm and 35,000 ppm(original) for potentiostatic deionization using 8 DC volt. As thepotential developed across the cells reaches 8V and current has declinedto a steady value, the deionization is terminated. Then, the residualenergy of the module after deionization performed on each solution isdischarged to an electronic load. Recovery efficiency of each energyextraction is calculated and listed in Table 1: TABLE 1 RecoveryEfficiency of the Residual Energy after CDI Energy Input EnergyRecovered Efficiency Seawater (ppm) (Joule) (Joule) (%) 20,000 3.42 0.226.5 35,000 5.27 0.98 18.5

[0034] Energy transfer in the 5,000 ppm seawater is too little to bemeasured. It appears that the recovery efficiency is higher with highersalt content.

EXAMPLE 2

[0035] The same CDI module as Example 1 is fully charged in 35,000 ppmseawater as Example 1. Afterwards, the residual energy is used to chargetwo commercial supercapacitors, and Table 2 shows the charged status thecapacitors, TABLE 2 Residual Energy of CDI Stored in SupercapacitorsSupercapacitor Voltage Developed Peak Current Specification (V)Delivered (A) 2.5 V × 20 F  1.9 4.1 2.5 V × 100 F 0.45 9.5

[0036] As shown in Table 2, the residual energy after CDI can be savedfor practical applications, and supercapacitors are well suited for theapplications.

EXAMPLE 3

[0037] The same CDI module as Example 1 is fully charged in 35,000 ppmseawater using a constant current of 5A. Immediately after thetermination of charge, the module is discharged to an electronic loadwhere a peak current of 39A is measured. Therefore, the CDI modulebehaves as a power converter for the peak current is much higher thanthe charge current.

EXAMPLE 4

[0038] A new CDI module is prepared by connecting 32 pieces electrodesof 6 cm×5 cm×0.35 mm in parallel to form one anode and one cathode. Theelectrodes use the same activated carbon as Example 1 as theelectrosorptive medium. The module is used for directly removing ions ofa waste liquid with a salt content of 122,000 ppm from a dye factory. Ineach cycle of process, the module is applied 3 DC volt for 5 minutes fordeionization, then the module is discharged quantitatively to anelectronic load with the module immersed in a regeneration medium, whichis DI water, in a separate container. Only the first six consecutivecycles of deionization and regeneration is shown in Table 3. TABLE 3Purification of a 122,000 ppm Waste Liquid by Recurrent Deionization andRegeneration Original Liquid Regeneration Liquid # (ppm) Δ ppm (ppm) Δppm 1 116,500 5,500  7,000 — 2 110,000 6,000 14,200 6,500 3 105,0005,000 21,100 6,900 4 101,000 4,500 27,750 6,650 5  95,500 5,500 33,0005,250 6  89,500 6,000 38,000 5,000

[0039] Theoretically, column 3 and column 5 of Table 3 should containthe same numbers the discrepancy may be due to cross contaminationand/or measurement errors. Nevertheless, Table 3 clearly demonstratesthat the CDI module in conjunction with the recurrent deionization andregeneration can directly and continuously purify liquids with extremelyhigh salt content. Furthermore, the amount of ions removed in each cycleis significant indicating that the present invention is a very usefulseparation technique.

[0040] On the other hand, when the deionizer of this invention is usedas a power converter, the electrolyte used in the power converter maycontain cations selected from the group consisting of H⁺, NH₄ ⁺, alkalimetal, alkali earth metals, transition metals, and the combinationsthereof. The electrolyte may contain anions selected from the groupconsisting of OH⁻, halides, NO₃ ⁻, ClO₄ ⁻, SO₃ ²⁻, SO₄ ²⁻, PO₄ ³⁻, andthe combinations thereof. In addition, the electrolyte may use a solventselected from the group consisting of water, methanol, ethanol, acetone,acetonitrile, propylene glycol, propylene carbonate, ethylene carbonate,and the combinations thereof. A protection case is also required tohermetically seal the electrode module in the power converter.

[0041] The above description in conjunction with various embodiments ispresented only for illustration purpose. There are many alternatives,modifications and variations that are apparent to persons skilled in theart in light of foregoing detailed description. It is intended toinclude all such alternatives in the spirit and scope of the appendedclaims.

What is claimed is:
 1. A deionizer with energy recovery for deionizing aliquid, comprising: at least one electrode module that comprises ananode, a cathode and an insulating spacer between the anode and thecathode; a DC power source for supplying electricity to the electrodemodule to remove ions from the liquid by electrosorption fordeionization; a regeneration part for discharging the ions from theelectrode module; a load for extracting energy from the electrode moduleand thereby restoring the electrode module to cleanliness forregeneration; and a mechanical setup for continuously switching theelectrode module between the liquid and the regeneration part.
 2. Thedeionizer of claim 1, further comprising a microprocessor for regulatingmaneuvers of the DC power source, the mechanical setup and the load. 3.The deionizer of claim 1, comprising a plurality of electrode modules,wherein the DC power source supplies electricity to some of theelectrode modules for deionization, and the load extracts energy fromthe electrode modules that have been used for deionization forregeneration.
 4. The deionizer of claim 3, wherein the deionization andthe regeneration are engaged continuously and alternatively to a firstpart of the electrode modules and a second part of the electrodemodules.
 5. The deionizer of claim 1, wherein the electrode modulecontains a plurality of electrodes that are open to the surroundings,wherein multiple pairs of electrodes are stacked and connected inparallel or in series to form the anode and the cathode and theinsulating spacer is inserted between every two electrodes to preventelectrical short and to provide the liquid free access to theelectrodes.
 6. The deionizer of claim 1, wherein the electrode modulecontains an anode, a cathode and two insulating separators spirallywound into an open roll where the liquid have free access to theelectrodes.
 7. The deionizer of claim 1, wherein the load also serves asan energy storage device.
 8. The deionizer of claim 7, wherein theenergy storage device is selected from the group consisting ofsupercapacitors, ultracapacitors and electric double layer capacitors.9. The deionizer of claim 7, wherein the regeneration of the electrodesis conducted by discharging residual energy of the electrodes to theenergy storage device.
 10. The deionizer of claim 1, wherein theelectrodes have electrosorptive materials using activated carbonprepared from one precursor selected from the group consisting ofcoconut shell, pitch, coal, polyurethane, polyacrylonitrile (PAN) andcombinations thereof.
 11. The deionizer of claim 1, wherein theelectrodes use carbon nanotube (CNT) as an electrosorptive material. 12.The deionizer of claim 1, wherein the anode uses titanium foil as asubstrate for conducting electrons.
 13. The deionizer of claim 1,wherein the cathode uses electronically conductive foil as a substratefor conducting electrons, the electronically conductive foil comprisinga material selected from the group consisting of aluminum, copper andtitanium.
 14. The deionizer of claim 1, wherein the insulating spacer isin the form of screen, mesh, net, network, web or comb.
 15. Thedeionizer of claim 1, wherein the insulating spacer comprises a materialselected from the group consisting of PE, PP, PVC, Teflon and Nylon. 16.The deionizer of claim 1, wherein a width of the insulating spacer isless than 0.2 mm.
 17. The deionizer of claim 1, wherein the DC powersource is selected from the group consisting of rectified AC, batteries,solar cells, and fuel cells.
 18. The deionizer of claim 1, wherein themechanical setup is a carousel or a Ferris wheel.
 19. The deionizer ofclaim 1, wherein the deionization is operated by a DC voltage of 3V orless.
 20. The deionizer of claim 1, wherein the regeneration isconducted in pure liquids, waste liquids, or seawater.
 21. The deionizerof claim 1, wherein a purified liquid and electricity are co-generated.22. A power converter, comprising: an electrode module containing ananode, a cathode and at least one ionically conductive spacer interposedbetween the anode and the cathode to prevent electrical short and tomaintain ion transfer between the electrodes; an electrolyte forproviding anions and cations for reversible adsorption and desorption onthe electrodes; and a protection case for hermetically sealing theelectrode module.
 23. The power converter of claim 22, wherein theelectrode module containing a plurality of electrodes that are stackedand connected in parallel or in series to form the anode and thecathode, while the ionically conductive spacer is interposed betweenevery two electrodes.
 24. The power converter of claim 22, wherein theanode, the cathode and two ionically conductive spacers spirally woundinto a roll.
 25. The power converter of claim 22, wherein theelectrolyte has a salt content of 5,000 ppm or higher.
 26. The powerconverter of claim 22, wherein the electrolyte contains cations selectedfrom the group consisting of H⁺, NH₄ ⁺, alkali metal, alkali earthmetals, transition metals, and combinations thereof.
 27. The powerconverter of claim 22, wherein the electrolyte conains anions selectedfrom the group consisting of OH⁻, halides, NO₃ ⁻, ClO₄ ⁻SO₃ ²⁻, SO₄ ²⁻,PO₄ ³⁻, and combinations thereof.
 28. The power converter of claim 22,wherein the electrolyte uses a solvent selected from the groupconsisting of water, methanol, ethanol, acetone, acetonitrile, propyleneglycol, propylene carbonate, ethylene carbonate, and combinationsthereof.